Negative Sign Amount on Multiplayer

In a vanilla server, on Creative as OP, I am able to get a negative amount of signs.

Run this command in an Impulse Command Block:

/give @p sign 1 0 {BlockEntityTag:{Text1:"{text:\"This is a\",color:\"light_purple\",clickEvent:{action:\"run_command\",value:\"/give @p diamond_chestplate\"}}",Text2:"{text:\"boss sign\",color:\"gold\",clickEvent:{action:\"run_command\",value:\"/give @p diamond_leggings\"}}",Text3:"{text:\"because \",color:\"dark_green\",clickEvent:{action:\"run_command\",value:\"/give @p diamond_boots\"}}",Text4:"{text:\"I'M GOOD!\",color:\"dark_red\",clickEvent:{action:\"run_command\",value:\"/give @p diamond_sword\"}}"},display:{Name:"Custom Sign"}}

Place a button on the block itself and push it.

Either place the sign to drop to 0 or SHIFT-CLICK when placing to drop into the negatives.